342 EEV. A. E. EATON ON RECENT EPHEMERID.E OK MAYFLIES. 



Plate L. 



Siphlurus lacustris, figs. 1, 4-6, & 9-19; aud a nameless Portuguese species, figs. 2, 3, 7, 8, & 20-26. 

 Nymphs. Figures all enlarged. — 1. Dorsal view of ^ insect of very advanced grade at rest, 

 with tracheal branchiae spread; the legs not in pci'spective. 2. The same view of a ? of rather 

 younger grade of another species, with the tracheal branchiae depressed. 3. Ventral view of 

 head and body of the same. 4. Side view of head and part of thorax, x 8 diam. 5. Antenna, 

 X 30 diam. 6. Exterior of labrum, x 35 diam. 7. Right mandible with tendon attached, 

 X 35 diam. 8. Left mandible, x 35 diam. 9. The same, with the tendon, placed to display 

 the fangs, x 30 diam. 10. First maxilla and palpus, x 45 diam. [The joining above the 

 prop of the palpus is distended witli fluid accidentally.] 11. Underside or exterior view of 

 labium, 2nd maxillfe, and palpi. 12. Partial view of the same reversed. 13. Dorsal view of 

 tongue and paraglossa;, x 35 diam. 14-16. Legs numbered successively from the foremost, 

 X 16 diam. 17-19. Right tracheal branchise of the 1st, 3rd, and 7th abdominal pairs of 

 £(. lacustris, x 25 diam. 20-26. Right tracheal branchise of the abdomen, one of every pair, 

 of the other species, x 15 diam. [S. lacustris in fluid; the other species in alcohol.) 



Plate LI. 



Oniscigaster Wakefieldi. Nymph. 



Figs. 1-23, all enlarged. — 1. Dorsal view of ^ insect about | grown, placed in a conventional 

 attitude. 2. Ventral view of head and body of the same. 3. Side view of head and part of 

 thorax, x 8 diam. 4. Front view of the head from above, x 8 diam. 5. The same from 

 below, x 8 diam. 6. Antenna, x 30 diam. 7. Exterior of labrum, x 30 diam. 8. Right 

 mandible with tendon attached, x 30 diara. 9. Left ditto. 10. First maxilla and palpus, x 

 30 diam. 11. Underside of labium, 2nd maxilhe, aud palpi, x 30 diam. 12. Dorsal view of 

 tongue and paraglosste, x 30 diam. 13-15. Legs numbered successively from the foremost, 

 X 11 diam. 10-21. Right tracheal branchiae of the abdomen, one of every pair, numbered 

 consecutively from the foremost, x 11 diam., in outline. 22 & 23. Finished di-awings of the 

 1st and 2nd of the same, x 20 diam., with the adjoining jjleura. (In alcohol.) 



Plate LI I. 



Ba-tisca obesa. Last slough cast by (J nymph. 



Figs. 1-14, all enlarged. — 1. Dorsal view of slough. [The antennae were originally represented in 

 this figure ; but as they are out of sight when the insect is alive, they were erased in the proving, 

 and only a very faint indication of the left antenna was allowed to remain.] 2. Ventral 

 view of head and body of the same. 3. Side view of head and part of thorax, with the 

 antenna partly removed. 4. Antenna, x 75 diam. 5. Exterior of labrum, x 35 diam. 

 6. Right mandible Avith part of tendon, x 60 diam. 7. Left ditto. 8. First maxilla and 

 palpus, with membrane attached to the stipes, x 60 diam. 9. Underside of labium, 2nd 

 maxillae and palpi, mentum, and hypopharynx, x 35 diam. 10. Dorsal view of tongue and 

 paraglossffi, x 35 diam. 11-13. Right legs numbered successively from the foremost, X 19 

 diam. 14. Underside of the right and median caudal setae, with part of the extremity of the 

 abdomen, x 25 diam. (Slough scalded.) 



